当对数据数组进行操作时，PDO是否真的比mysql_ *快？

Question

Ive recently upgraded my mind from mysql_* to PDO, and I have one simple question:

Is PDO really that much more efficient that the use of a prepared statement and an execute in a for-each loop is quicker than a single call in mysql with multiple values in it?

For example if I have an array of 5 names, putting these in an execute command in a for loop operating on an 'insert' prepared statement - is calling this 5 times going to be quicker in computational speed that one call using the old mysql with all 5 values in a single query? Or is it preferred due to security rather than speed alone?

Answer 1

The meaning and significance of native prepared statements (which you call "PDO") is overlooked and misjudged by everyone.

The speed benefit, everyone talking about so much, in reality can be achieved extremely rare, and often unnoticeable at all. Especially in the area of web-development with PHP which PDO belongs to.
Also note that whatever speed benefit belongs to the query parsing only - no such matters like index rebuilding or time required to find a record to update ever affected by prepared statements.

So, speaking of numbers like five, don't bother yourself with this "once-prepare-multiple execute" thing. It is not what PDO is about. PDO does two essential things, which makes it preferred over two other possible extensions:

• it supports prepared statements in general, allowing data in the query not directly but via placeholder. This is the only reason why you should use PDO or similar lib (although you can easily make even old mysql ext to support prepared statements, but PDO offers it out of the box)
• it makes such support not as painful as mysqli

Turning back to your question:

1. You can use either way you like. Just remember that multiple inserts are better to be wrapped in a transaction, due to default settings of the modern DB engines
2. No matter which way you choose, any dynamical value should be added into query via placeholders only . If you still not convinced, you are welcome to read an article I wrote on the matter (which is still incomplete, but have a through explanation on the real meaning of prepared statements) .

PS. There is also one minor benefit of native prepared statements, often forgotten (becaulse seldom demanded) - if native prepared statement were used (and backed by msqlnd driver), the data returned is already formatted according to its type.

Answer 2

One query that fetches 5 rows will probably be quicker than 5 separate calls, so you are comparing apples and oranges.

When executing the same query, the performance will be similar too. The (small) performance advantage that PDO has, is that queries with parameters are supposed to be better cachable. When querying customer 3 and customer 5 , the query will be cached as two different queries, while only the id is different. By using parameters, the database might cache the query in a smarter way, so a second call with a different input doesn't need to go through the query optimizer and such.

That said, apart from the performance advantage, PDO is also safer (when actually using paramteres), and in the end easier. It may look more complex at first, but it is easier to do right, because without using parameters, you will need to do all the escaping yourself, risking dangerous bugs.

By the way, you can also build a query with a variable number of parameters, and bind a value to each of them in a loop, so with PDO you could still perform the single insert query for 5 rows, although it will need a bit puzzling and a bit of extra code.